Toán Lớp 6: Tính hợp lí nếu có thể: a, ( -423 ) – ( 358 – 123 ) + ( 34 – 542 ) b) 26 . 394 + ( -26 ) . 37 – 43 . ( -26 )
a)(-423)-(358-123)+(34-542)=(-423)-358+123+34-542=(-423+123)-(358+542)+34=-300-900+34=-1200+34=-1166 b)26.394+(-26).37-43.(-26)=(-26).(-394)+(-26).37-43.(-26)=(-26)(-394+37-43)=(-26).(-400)=10400
a)( -423 ) – ( 358 – 123 ) + ( 34 – 542 ) =(-423)-358+123+34-152 =(-423+123)-(358+542)+34 =(-300)-(900)+34 =-1166 b)26 . 394 + ( -26 ) . 37 – 43 . ( -26 ) =26.394+26.(-37)-(-43).26 =26.394+26.(-37)+43.26 =26.[394+(-37)+43] =26.400 =10400
=(-423)-358+123+34-542
=(-423+123)-(358+542)+34
=-300-900+34
=-1200+34
=-1166
=(-26).(-394)+(-26).37-43.(-26)
=(-26)(-394+37-43)
=(-26).(-400)
=10400